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R J Melton

Publications and source records attributed to R J Melton.

12 recordsLinked to original sources
PubMed2000

The alpha4 isoform of the Na,K-ATPase is expressed in the germ cells of the testes.

In addition to the three isoforms of the catalytic subunit of the Na, K-ATPase originally identified (alpha1, alpha2, and alpha3), a fourth alpha polypeptide (alpha4) has recently been found in mammalian cells. This novel alpha-subunit of the Na,K-ATPase is selectively expressed in male gonadal tissues. In the testes, alpha4 is functionally active and comprises approximately half of the Na, K-ATPase activity of the organ. At present, the pattern of expression of the alpha4 polypeptide within the cells of the male gonad is unknown. By in situ hybridization, immunocytochemistry, and the ouabain inhibition profile of Na,K-ATPase activity, we show that the alpha4-subunit is expressed in the germ cells of rat testes. The highest amounts of the isoform are found in spermatozoa, where it constitutes two thirds of the Na,K-ATPase activity of the gametes. The other Na pump present in the cells is the ubiquitously expressed alpha1 polypeptide. The characteristic localization of alpha4 in the gonad is further supported by the drastic reduction of the polypeptide in mice that are infertile as a consequence of arrest in maturation of the germ cells. In addition, GC-1spg cells, a murine cell line derived from testis spermatogonia, also contain the Na, K-ATPase alpha4 polypeptide. However, the level of expression of the isoform in these cells is much lower than in the spermatozoa, a fact that may depend on the limited ability of the GC-1spg cells to differentiate in vitro. The particular expression of the Na,K-ATPase alpha4 isoform we encounter and the specific enzymatic properties of the polypeptide suggests its importance for ionic homeostasis of the germ cells of the testes.

Animals↗
PubMed1999

Functional characterization of a testes-specific alpha-subunit isoform of the sodium/potassium adenosinetriphosphatase.

Different isoforms of the sodium/potassium adenosinetriphosphatase (Na,K-ATPase) alpha and beta subunits have been identified in mammals. The association of the various alpha and beta polypeptides results in distinct Na,K-ATPase isozymes with unique enzymatic properties. We studied the function of the Na,K-ATPase alpha4 isoform in Sf-9 cells using recombinant baculoviruses. When alpha4 and the Na pump beta1 subunit are coexpressed in the cells, Na, K-ATPase activity is induced. This activity is reflected by a ouabain-sensitive hydrolysis of ATP, by a Na(+)-dependent, K(+)-sensitive, and ouabain-inhibitable phosphorylation from ATP, and by the ouabain-inhibitable transport of K(+). Furthermore, the activity of alpha4 is inhibited by the P-type ATPase blocker vanadate but not by compounds that inhibit the sarcoplasmic reticulum Ca-ATPase or the gastric H,K-ATPase. The Na,K-ATPase alpha4 isoform is specifically expressed in the testis of the rat. The gonad also expresses the beta1 and beta3 subunits. In insect cells, the alpha4 polypeptide is able to form active complexes with either of these subunits. Characterization of the enzymatic properties of the alpha4beta1 and alpha4beta3 isozymes indicates that both Na,K-ATPases have similar kinetics to Na(+), K(+), ATP, and ouabain. The enzymatic properties of alpha4beta1 and alpha4beta3 are, however, distinct from the other Na pump isozymes. A Na, K-ATPase activity with similar properties as the alpha4-containing enzymes was found in rat testis. This Na,K-ATPase activity represents approximately 55% of the total enzyme of the gonad. These results show that the alpha4 polypeptide is a functional isoform of the Na,K-ATPase both in vitro and in the native tissue.

Adenosine Triphosphate↗
PubMed1996

Processing goals, task interest, and the mood-performance relationship: a mediational analysis.

The authors examined the role of intrinsic interest in mediating the relationship among mood, processing goals, and task performance. Participants in induced happy, neutral, or sad moods generated similarities and differences between TV shows using performance-based, enjoyment-based, or no stop rule (cf. L.L. Martin, D.W. Ward, J.W. Achee, & R.S. Wyer, 1993). Pretask interest and both quantitative (time spent, number generated) and qualitative (creativity) performance were assessed. Happy participants spent more time and generated more items than other participants when using an enjoyment-based stop rule but spent less time and generated fewer items when using a performance-based stop rule. Happy participants also expressed greater pretask interest and were more creative than other participants regardless of stop rule. Regression-based path analyses indicated that pretask interest partially mediated the effects of mood on quantitative performance but not on creativity.

Affect↗
PubMed1994

The capacity-building approach to intervention maintenance implemented by the Stanford Five-City Project.

Increasingly, agencies supporting community health promotion interventions require participating communities and evaluators to specify how the intervention will be maintained once agency funding ends. The Stanford Five-City Project (FCP) implemented two different strategies to maintain its heart disease education program, with the second strategy designed to overcome the barriers to implementation that were encountered by the first. This paper provides a practice-oriented description of the initial 'community network' maintenance strategy of the FCP, the barriers that were encountered as this network strategy was implemented, the alternative 'capacity-building' strategy directed at local health educators and the successful implementation of this alternative. Also discussed are the community organization issues underlying the shift in intervention maintenance strategies and the specific components of the capacity-building strategy, including its focus on health educators, and its application of a training of trainers model and cooperative learning methods to provide professional development, technical assistance and other resources to a target group of community health educators. Our experience indicates that capacity-building is a viable method for intervention maintenance and that it may also facilitate efforts to disseminate model health promotion programs to communities lacking experience in community health promotion intervention.

California↗
PubMed1991

Image, issues, and ideology: the processing of information about political candidates.

Ss watched a videotaped nonpolitical speech by a male political candidate that conveyed either a favorable or an unfavorable image. Then they heard an excerpt of a radio program in which the candidate was described as holding either conservative positions or liberal positions on a series of specific issues. The impact of the candidate's speech on evaluations of him decreased over time. However, Ss used the speech as a basis for judgment only when the candidate's issue stands had unfavorable implications. When Ss learned the candidate's issue stands 24 hr after they heard the speech, they based their evaluations on their personal agreement with these stands. When Ss learned the candidate's issue positions immediately after the speech, however, they based their evaluations on the ideological implications of the issue stands instead.

Adult↗
PubMed1981

Revising the rural hospital disaster plan: a role for the EMS system in managing the multiple casualty incident.

Much of the effort in disaster planning has been directed toward large-scale, war-related, or major natural disasters. We helped test a rural community's disaster plan in a simulated airport accident, and concluded that this plan was not the most effective for providing the triage and stabilization in the field that are essential to the management of this type of accident. This communication argues for the development of an alternative model of response involving the "escalation" of the everyday emergency medical services system. We believe this will provide more rapid and effective allocation of the rural community's limited medical resources in the management of the multiple casualty incident.

Aircraft↗